Photocatalytic reduction of CO2 with H2O over modified TiO2 nanofibers: Understanding the reduction pathway

Sarkar, Anjana; Gracia‐Espino, Eduardo; Wågberg, Thomas; Shchukarev, Andrey; Mohl, Melinda; Rautio, Anne-Riikka; Pitkänen, Olli; Sharifi, Tiva; Kordás, Krisztián; Mikkola, Jyri‐Pekka

doi:10.1007/s12274-016-1087-9

Cited by 63 publications

(41 citation statements)

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“…In addition, the presence of reductants providing protons to react with the adsorbed CO 2 on a photocatalyst surface and electrons to form products assists the process of CO 2 conversion by lowering the required input energy in comparison to the absence of reducing agents, in which the reduction of CO 2 proceeds by a photocatalyst alone and is much more difficult because of the high stability of inert CO 2 . Therefore, photoreduction of CO 2 is commonly conducted with a reductant, such as H 2 or/and H 2 O, making the conversion of CO 2 into fuels more feasible and more efficient from the view point of consumed energy [32,33]. In a CO 2 (g)/H 2 O(g/L) or CO 2 (g)/H 2 (g) system, photoexcited electrons are generated under light irradiation and are transferred, and then they react with the adsorbed CO 2 on the photocatalyst surface along with protons provided by the reducing agents to yield the reduced products.…”

Section: Fundamentals Of Co 2 Photocatalytic Reductionmentioning

confidence: 99%

Recent Advances in TiO2-Based Photocatalysts for Reduction of CO2 to Fuels

Nguyen

et al. 2020

Nanomaterials

161

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Titanium dioxide (TiO2) has attracted increasing attention as a candidate for the photocatalytic reduction of carbon dioxide (CO2) to convert anthropogenic CO2 gas into fuels combined with storage of intermittent and renewable solar energy in forms of chemical bonds for closing the carbon cycle. However, pristine TiO2 possesses a large band gap (3.2 eV), fast recombination of electrons and holes, and low selectivity for the photoreduction of CO2. Recently, considerable progress has been made in the improvement of the performance of TiO2 photocatalysts for CO2 reduction. In this review, we first discuss the fundamentals of and challenges in CO2 photoreduction on TiO2-based catalysts. Next, the recently emerging progress and advances in TiO2 nanostructured and hybrid materials for overcoming the mentioned obstacles to achieve high light-harvesting capability, improved adsorption and activation of CO2, excellent photocatalytic activity, the ability to impede the recombination of electrons-holes pairs, and efficient suppression of hydrogen evolution are discussed. In addition, approaches and strategies for improvements in TiO2-based photocatalysts and their working mechanisms are thoroughly summarized and analyzed. Lastly, the current challenges and prospects of CO2 photocatalytic reactions on TiO2-based catalysts are also presented.

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Section: Fundamentals Of Co 2 Photocatalytic Reductionmentioning

confidence: 99%

Recent Advances in TiO2-Based Photocatalysts for Reduction of CO2 to Fuels

Nguyen

et al. 2020

Nanomaterials

161

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“…We hypothesize that the photocatalytic reduction of CO 2 takes place through surface formates. The first step is the activation of CO 2 , in which a radical anion (CO 2 *− ) is formed [57,58,61] On the other hand, UV irradiation can also generate e − (Ti 4+ ) electrons, which results in the formation of carboxylates in the presence of CO 2 [48,68].…”

Section: Photocatalytic Reaction Of Co 2 + H 2 On Au/tntmentioning

confidence: 99%

“…A further possible mechanism of the CO formation is the decomposition of the surface formate to CO and a surface OH group (Eq. 18) [62,68].…”

Section: Photocatalytic Reaction Of Co 2 + H 2 On Au/tntmentioning

confidence: 99%

Beyond Nanoparticles: The Role of Sub-nanosized Metal Species in Heterogeneous Catalysis

Kiss

Kukovecz

2019

Catal Lett

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Titanate nanostructures are of great interest for catalytic applications because their high surface area and cation exchange capacity create the possibility to achieve high metal dispersion. Ion exchange allows titanate nanostructures to incorporate metal adatoms in their framework. Consequently, the curved layers contain a large amount of defect sites, typically oxygen vacancies and Ti 3+ centers, which can make them promising photocatalysts, because the defect sites can trap photoelectrons or holes extending the lifetime of the excited state. Due to the large amount of defects, titanate nanotubes (TNT) can stabilize sub-nanosized gold clusters, presumably in Au 25 form. This perspective summarizes the previous results obtained in the photocatalytic transformation of methane in which the size of gold nanoclusters plays an important role. Photocatalytic measurements revealed that methane is active towards photo-oxidation. Methane transforms mainly into hydrogen and, to a lesser extent, to ethane and ethanol. Based on recent additional results, we stress here that gold clusters (Au 25) may be directly involved in the photo-induced reactions, namely in the direct activation of the methane/Au 25 δ+ complex during irradiation. Another new finding is that gold nanoparticles supported on TNT exhibit high catalytic activity in CO 2 hydrogenation. Our results revealed fundamental differences in the reaction schemes as the products of the two routes are CO (thermal process) and CH 4 (photocatalytic route), indicating the importance of photogenerated electron-hole pairs in the reaction. The presence of gold nanoparticles on the surface has been found to have multiple roles. On the one hand, gold in nano and sub-nano sizes promotes the adsorption and scission of reactants, important for both types of reactions. On the other hand, the gold-support interface forms a rectifying Schottky contact that helps in the separation of photogenerated carriers, thus improving the utilization of electrons and holes in the reduction and oxidation steps, respectively. Furthermore, gold ions (Au +), in the cationic sites of the titanate lattice promote the photocatalytic transformation of formate (which is one of the intermediates), thus advancing the reaction further towards the fully reduced product. The explored reaction schemes may pave the road towards novel catalytic materials that can solve challenges associated with the activation of CH 4 and CO 2 and thus contribute to green chemistry.

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“…Therefore, the ability to harness the power of CO 2 on a large scale and integrate it back into the utilization cycle as a sustainable form of energy production is highly desirable. Among the various renewable projects to date, the photocatalytic reduction of CO 2 into energy-bearing products has garnered interdisciplinary research attention to mitigate the evergrowing CO 2 concentration and to meet the long-term worldwide energy demands without utilizing further CO 2 -generating power resources [6][7][8][9][10][11][12][13][14][15]. In this context, photocatalysis, a wellorchestrated mimic of natural photosynthesis, for direct conversion of solar energy to chemical energy, presents an opportunity to kill these two birds with one stone [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%